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Exploring the Nature of Little Red Dots: Constraints on AGN and Stellar Contributions from PRIMER MIRI Imaging

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arxiv 2411.12005 v2 pith:BT4DN3F3 submitted 2024-11-18 astro-ph.GA

Exploring the Nature of Little Red Dots: Constraints on AGN and Stellar Contributions from PRIMER MIRI Imaging

Gene C. K. Leung , Steven L. Finkelstein , Pablo G. P\'erez-Gonz\'alez , Alexa M. Morales , Anthony J. Taylor , Guillermo Barro , Dale D. Kocevski , Hollis B. Akins
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Adam C. Carnall \'Oscar A. Ch\'avez Ortiz Nikko J. Cleri Fergus Cullen Callum T. Donnan James S. Dunlop Richard S. Ellis Norman A. Grogin Michaela Hirschmann Anton M. Koekemoer Vasily Kokorev Ray A. Lucas Derek J. McLeod Casey Papovich L. Y. Aaron Yung
This is my paper
classification astro-ph.GA
keywords stellarmodelmiricontinuumgalaxylrdsagnscontribution
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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JWST has revealed a large population of compact, red galaxies at $z>4$ known as Little Red Dots (LRDs). We analyze the spectral energy distributions (SEDs) of 95 LRDs from the JWST PRIMER survey with complete photometric coverage from $1-18\ \mu$m using NIRCam and MIRI imaging, representing the most extensive SED analysis on a large LRD sample with long-wavelength MIRI data. We examine SED models in which either galaxy or active galactic nucleus (AGN) emission dominates the rest-frame UV or optical continuum, extracting physical properties to explore each scenario's implications. In the galaxy-only model, we find massive, dusty stellar populations alongside unobscured, low-mass components, hinting at inhomogeneous obscuration. The AGN-only model indicates dusty, luminous AGNs with low hot dust fractions compared to typical quasars. A hybrid AGN and galaxy model suggests low-mass, unobscured galaxies in the UV, with stellar mass estimates spanning $\sim$2 dex across the different models, underscoring the need for caution in interpreting LRD stellar masses. With MIRI photometry, the galaxy-only model produces stellar masses within cosmological limits, but extremely high stellar mass densities are inferred. The hybrid model infers highly overmassive black holes exceeding those in recently reported high-redshift AGNs, hinting at a partial AGN contribution to the rest-optical continuum or widespread super-Eddington accretion. Our findings highlight the extreme conditions required for both AGN or galaxy dominated scenarios in LRDs, supporting a mixed contribution to the red continuum, or novel scenarios to explain the observed emission.

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Cited by 8 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Misaligned or chaotic? A strong break of axial symmetry in the local LRD J1025 revealed with VLT/FORS2 spectropolarimetry

    astro-ph.GA 2026-07 accept novelty 7.0

    The local Little Red Dot J1025 shows a 48° polarisation-angle offset between continuum and broad H-alpha, requiring broken axial symmetry.

  2. Discovery of Multiply Ionized Iron Emission Powered by an Active Galactic Nucleus in a z~7 Little Red Dot

    astro-ph.GA 2025-09 conditional novelty 6.0

    The z=6.68 Little Red Dot THRILS 46403 shows a 4.5 sigma [FeVII] line, the first robust coronal-line detection among z>5 LRDs, plus narrow Balmer absorption, supporting an AGN with direct sightlines to gas at or beyon...

  3. Compact, AGN-hosting Dwarf Galaxies with "Little Red Dots"-like SEDs in the Local Universe

    astro-ph.GA 2026-05 unverdicted novelty 5.0

    Local compact AGN-hosting dwarf galaxies with V-shaped SEDs are more evolved than high-redshift Little Red Dots, indicating distinct formation pathways.

  4. Evidence of violation of Case B recombination in Little Red Dots

    astro-ph.GA 2025-10 conditional novelty 5.0

    In one of seven Little Red Dots, the broad Hδ/Hα ratio is more than 5σ below the Case B prediction, signalling a breakdown of standard recombination in very dense gas.

  5. The mechanism for creating "dynamical gravastar" black hole mimickers also explains formation of "little red dots"

    gr-qc 2025-09 unverdicted novelty 5.0

    A phase transition to negative energy density in relativistic matter forms dynamical gravastars and also powers little red dots through latent energy release and extreme gravitational redshift.

  6. Evolution of Size, Mass, and Density of Galaxies Since Cosmic Dawn

    physics.gen-ph 2025-10 reject novelty 4.0

    Under the author's CCC+TL cosmology, galaxy effective radii are larger by roughly (1+z)^0.93, reducing the inferred density and mass of early galaxies.

  7. Ultra High-Redshift or Closer-by, Dust-Obscured Galaxies? Deciphering the Nature of Faint, Previously Missed F200W-Dropouts in CEERS

    astro-ph.GA 2025-02 conditional novelty 4.0

    New F200W-dropout candidates in CEERS include three massive dusty dwarfs at 2<z<3 and five sources with bimodal redshift PDFs favoring either z>15 or z<1.5 extreme dust.

  8. The mechanism for creating "dynamical gravastar" black hole mimickers also explains formation of "little red dots"

    gr-qc 2025-09 unverdicted novelty 3.0

    A single phase transition mechanism to negative energy density explains both dynamical gravastars and little red dots through latent energy and high gravitational redshift.